For those who don't know, the Oxford comma is the use of a comma before the conjunction in a list of three or more separate nouns. For instance, in the phrase 'red, blue, and yellow', the Oxford comma is the one that comes directly after the word "blue". So if you were to remove the Oxford comma, the phrase would become 'red, blue and yellow'.
Now, my opinion is that the addition of the Oxford comma not only looks better (because leaving it out suggests a stronger visual connection between the last two objects in the list than is actually present), but also better matches human speech pattern and resolves the possible confusion of the last two objects appearing as a apposition to the first. (Ex. 'The group included two women, Jack and John.' where the absence of the Oxford comma can be seen to suggest that the two girls are Jack and John. The addition of the Oxford comma would make the phrase 'The groups included two women, Jack, and John.', which makes it clear that the 'two women' and 'Jack and John' are separate entities.) It also clarifies groups in phrases where a conjunction is already used in the list. (Ex. 'My usual breakfast is coffee, bacon and eggs and toast.' In this sentence, the lack of the Oxford comma makes it impossible to tell whether one of the foods is 'bacon and eggs' or if bacon is separate and 'eggs and toast' go together. An Oxford comma would solve this.)
In interest of having a fair debate, I also realized it would be fair to provide the counterargument to the use of the Oxford comma (I needed the help of Wikipedia, admittedly). The three main points against it seem to be that it adds unnecessary bulk when space is at a premium, is redundant in a simple list (because conjunctions can typically be understood to be separation enough), and that it actually can introduce ambiguity in some cases. (Ex. 'They went with a Tom, a farmer, and Bill.' In this case, it could be that there are only two people in the case that 'a farmer' is not introducing a new person but instead clarifying that Tom is a farmer. The removal of the Oxford comma would resolve this by making clear that three people were being mentioned)